The machining of flange surfaces of a wheel hub and especially the surface grinding thereof is important since those surfaces are attachment surfaces for the brake disks of wheel hubs which are provided with disk brakes.
When the flange surface is not planar to within a narrow tolerance and not exactly perpendicular to the axis of rotation of the wheel hub, the brake disk attached to the flange and rotating with the wheel hub has a certain degree of wobble and shows angular position-dependent offset movements in the axial direction that can be described as knocking or flapping. Indeed, even very slight angle-dependent offset movements or wobble can translate into vibration which is transmitted to the brake pedal and can be noticeable during the braking operation. Machining defects at the flange surface of the wheel hub become all the more noticeable and significant as the brake disk attached thereto is of larger diameter. The problem is, therefore, usually more noticeable on small transport-type vehicles or utility vehicles like pick-up trucks, heavier trucks and similar utility vehicles than it is for passenger-type vehicles like automobiles.
In conventional fabrication methods the surfaces of the wheel hub are finish-machined before the wheel bearings are mounted on the hub. Following mounting of the hub and the wheel bearing in a vehicle, as a unit, a problem with wobble can be discovered upon rotation of the wheel hub. Depending upon the particular vehicle, it is not uncommon to have a rotation-angle-dependent offset movement in the axial direction which is of the order of 40 to 60 .mu.m. That magnitude of offset or axial throw will give rise to detrimental wobble. With increasing diameter of the brake disk, the wobble is more severe. The axially offset movement, likewise which is rotation-angle dependent of the brake disk can amount to up to 100 .mu.m and magnitudes of this nature give rise to significant vibration at the brake pedal when the brake is actuated.